The present invention relates to an automatic film winding apparatus for use with cameras, and more particularly to an improved automatic film winding apparatus in which a sub-driving apparatus comprising a spring motor is provided in addition to a main diriving apparatus for film winding.
Conventionally, an electric motor, a spring motor and a gas pressure of a high pressure gas cylinder are used as a driving force source of the film winding apparatus for use with cameras.
However, the automatic film winding apparatus employing such a single driving force source as mentioned above has certain shortcomings. For example, an automatic film winding apparatus employing an electric motor requires at least a certain minimum power level, and increasing the size of the battery to increase the life of the battery for use with the film winding apparatus will cause an increase of the size of the apparatus or the weight thereof and the apparatus will become inconvenient for carrying by hand.
In the case of a film winding apparatus employing a spring motor, the driving force storage capacity of the spring motor is comparatively small so that rewinding the spring to provide the driving force is necessary after several frames of a film. Therefore, the spring motor is not suitable for a continuous photographing, and in order to increase the driving force storage capacity, the size and the weight of the film winding apparatus have to be increased, which makes the apparatus inconvenient for carrying by hand.
Furthermore, in the case of a film winding apparatus employing a high pressure gas cylinder, a mechanism for preventing leakage of gas and that for preventing destruction of the apparatus have to be provided in the apparatus, which makes the apparatus complicated in mechanism and requires a high accuracy of the size of of each part of the apparatus in order to maintain the gastightness of the apparatus. Accordingly, the production cost of the apparatus becomes high. Moreover, the high pressure gas cylinder is not easily available.